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FAQ or Answers to Frequently Asked Questions Section 32
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Please check "root" (faq$txt) file for acknowledgements.
This is a file containing answers, tips, hints and guidelines associated
with recurring questions asked by photographers. If you would like to
add a tidbit of knowledge to this list just send it to ANDPPH@rit.edu
who will gladly add it to this collection. For complete table of content
send message to ritphoto@rit.edu with FAQ$txt in the Subject: line
These files are available in SECTIONS.
This is Section 32 and its contents are listed below.
32.01 -< Manufacturers and Distributors of Rotating Panoramic Cameras >-
32.02 -< Several observations on rotating panoramic cameras >-
32.03 -< Comments on panoramic photography requirements >-
32.04 -< Pointers on drying Fiber Based papers >-
32.05 -< Dividing 1 gal E-6 for small batch processing >-
32.06 -< High Speed Photography Sample Exam - Questions and Answers >-
32.07 -< The Royal Photographic Society - Info >-
32.08 -< More panoramic photography material ... >-
32.09 -< How to determine the aperture and f# of a lens? >-
32.10 -< Pointers for including the moon in a photograph >-
32.11 -< Sun and Moon rise/set locator program retrievable from Net >-
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Note 32.01 -< Manufacturers and Distributors of Rotating Panoramic Cameras >-
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This is a list of US manufacturers and distributors of rotating camera type
panoramic cameras. Please send info on others to: andpph@rit.edu to update
this file.
Hulcherama - Charles Hulcher Company Globuscope - Globus Bros. Studio
909 "G" Street 44 W. 24th Street
Hampton, VA 23661-1717 New York, NY 10010
804-245-6190 212-243-1000
Alpa Rotocamera - HP Marketing SpinShot - Karl Heitz
216 Little Falls 34-11 62nd Street
Cedar Grove, NJ 07009 Woodside, NY 11377
201-857-0171 718-565-0004
Roundshot - Camerama
131 Newton Street
Weston, MA 02139
800-274-5722
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Note 32.02 -< Several observations on rotating panoramic cameras >-
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>Last week some one posted a message regarding a friends camera that makes
>10" x 4' negs. Sounds great! B&H advertises a similar camera called a
>"Spin-shot" I think it uses 35mm film and it rotates on its tripod mount
>to include a full 360 degree pan on each exposure. I think the negs it
>makes are the width of 4 reg frames. Has anyone ever used or seen this
>type of camera or a similar one from another manufacturer? Any comments
>or shared experiences would be appreciated.
I have two SpinShots ... bought them just before the price climbed to $2 per
degree. The camera is interesting but has many major limitations. At least mine
do. Fixed aperture for one ... so adjusting for lighting conditions is done by
using different film speeds (pretty novel, eh?)(I guess you also could use
fastest film plus ND filters). The camera is made of plastic and the plastic
latch on both of mine broke and cameras are now held together by tape or rubber
band. The film speed through the camera does change as the take up spool
diameter increases causing slight blurring at the ends of the film. Often this
is not really noticeable except under high magnification.
MUCH better is the Globuscope. A 35mm rotating panoramic camera also Made in
USA (as far as I know) and it is an all metal camera (except where metal would
not normally be used ... like lens!) and the camera's rotation rate can be
changed, it has a high quality lens, and various adjustments. The price tag is
in the $2,500 area however.
At the larger format end there is the Hulcherama. A camera made in Hampton, VA
by the Charles Hulcher Company. It is an excellent camera in my opinion. It is
set up for Mamiya 645 lenses but can be custom made to accept others (at higher
price). It can be readily ordered with provision to accept 35, 45 and 80mm
lenses. It takes 120 or 220 film. It has a pinch-drive system so film speed is
uniform. The rotation rate can be varied over a large range and the slit-size
is also adjustable giving you a large variety of exposure times. The price for
the camera body alone is in the $5,000 range.
There is the Alpa Rotocamera. A GREAT camera set up for a 100mm lens I think
and I also believe it has the capability for rising/falling lens. The camera is
a marvel of mechanical engineering and also made in Europe. It's price is high.
Beyond these there are the various Roundshot cameras made in Switzerland I
think. They come in 16mm, 35, 2 1/4 and even larger formats. They are
jewel-like in contruction and operation and their price tag reflects this. The
company that makes these cameras also now makes a "strip" enlarger which one
lab in Florida has purchased. Although amateurs such as myself have built such
enlargers much earlier (like 1975 or so) this is the first commercial example
of such an enlarger (although Itek built such a machine for the Air Force in
the late 60's I believe).
hmmmm ... did I leave anything out? If so just give me another "kick" ;-)
oh, yes .... if you want to read about "strip" cameras and home-made panoramic
and peripheral cameras you can find several articles at the ritphoto@rit.edu
mailserver site.
Just send e-mail to this address and say ARTICLES$txt in the subject line to
get a table-of-contents and brief synopsis of the articles available for the
asking along with instructions on how to retrieve them. These are only text
files so you'll have to imagine the pictures. The part of the site you will be
accessing is devoted to the PhotoForum mailing list (which is shared by/with
our school's program files) and if you make an error in requesting anything you
will be sent by default a file that tells you all the "stuff" available at the
site.
If you actually go looking in this place I hope you find something of use to
you! BTW ... some of this stuff is also available by anonymous FTP at
vmsftp.rit.edu under pub/ritphoto/photoforum
>I don't believe their strip enlarger is that new; if I recall correctly,
>they had this enlarger on the PhotoKina in Cologne (Germany) in '92 or '90.
>But I think Seitz itself was the only company at that time that could do
>those prints on a economic basis....and the number of labs in Europe having
>one right now is also quite limited I guess....similar to the camera itself.
very true ... OTOH Phil Foss of Eastman Kodak had made one in the early 80's
and mine was operating in the mid 70's I believe. The Itek enlarger was
designed for enlarging 70mm or 5" film that was exposed in aerial strip cameras
based on a design by Sonne of Chicago Aerial Industries who made the camera for
General Goddard I believe. Sonne and del Veccio who was a pioneer in
photofinish camera development in the mid 1930's cooperated in amking the
aerial version of the photofinish camera. This is pretty much the same as
making pictures of a wallpaper or the houses along a street (which I did over a
mile long stretch of a local avenue a couple of years ago... but which the
Globus brothers did almost 10 years ago by holding their camera still allowing
the handle to rotate)
>BTW, Seitz makes also pseudo (or 'inverse'?) panorama camera's, where the
>objects turns around instead of the camera. This is usefull for an 360
>degree image of a teacup for example. Another variant is a camera that runs
>parallel to the object, to make a distortionfree image of a wallpaper for
>example.
Indeed in the late 1800's at the British Museum strip cameras (or variations
thereof) were already used to make what some people call "rollout" photographs
of rotating vases and urns, etc. These pictures being possibly better referred
to as "peripheral" photographs. There was a company in England that made the
R.E. Engineers Periphery Camera which was actually a traversing back that could
be fitted to a 4x5 camera. The function of the moving back was to move the film
at a steady pace past a slit. The device also came with a precision turntable
and the whole thing could be mounted on a lathe-bed or similar for high
precision peripheral work onto sheet film. The price was very high but several
labs (notably the FBI lab in Washington) purchased one of these units. Steve
Morton in Australia made a back like this independently.
Also, Omega Timing (also Swiss?) has developed the technique of photofinish
photography to an "art" having not only film cameras, but also sheet film and
Polaroid cameras.
BTW, please note that this is not to diminish or otherwise dismiss Seitz's
contributions to the field but their products can probably more accurately be
called refinements to a very high order of precision of techniques that are
almost as old as photography itself. Maybe a better way to take these snippets
of info is as a brief review of the history of strip cameras! ;-)
And before I forget, there are many "amateurs" (lovers of the craft) who have
developed exquisite cameras and made wonderful photographs with them. I will
try to compile a listing of these individuals as best I know them but until the
project gets going I wanted to mention just this one:
Steven Morton, works at Monash University in Melbourne, Australia. His e-mail
address is Steven.Morton@sci.monash.edu.au
Others whose name popped into my head: Phil Foss, Jim Lipari, Charles Hulcher,
and E.O. Goldbeck. And among the swing-lens panoramic camera makers and
photographers: Tom Yanul, who works in Chicago and makes his own VERY large
format cameras that are maybe 20 inches tall by 6 feet long and cover 130 to
150 degrees or so.
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Note 32.03 -< Comments on panoramic photography requirements >-
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>if the film required for a panorama is in mm = 2 x Pi x focal length (mm)
>then if the camera does not rotate about its film plane but on a disk so that
>the film plane is say 100mm off the centre of rotation, should this additional
>radius be added to the fl of the lens to determine the correct film length??
The answer is no (but with caveats). As long as the subjects you are
photographing are very far away like when doing scenics it does not matter
much that the camera rotate about an axis other than the rear nodal point.
Once the subjects start to be closer than "infinity" then this factor needs
to be taken into account. The problem is that while you will be properly
correcting for subjects that are closer than infinity, those objects at
infinity now will be reproduced in distorted fashion. What is happening is
that the image velocity is no longer uniform for near and far objects.
If the camera rotates about the proper point there is no relative motion
between the image and the film ... they both move equally fast. If the
camera rotates about an axis closer to the film plane or even possibly
behind the film plane the consequence is that images of nearby objects will
appear to move past the slit in the camera faster then those far away. If
you do not compensate they will be reproduced "compressed" horizontally. The
objects at infinity will hardly change in speed no matter how far the camera
is from the axis of rotation. You could (theoretically) use the earth as the
device to turn the camera and make a panoramic photograph of the heavens
with not problem.
From Applied Photography by Arnold, Rolls and Stewart:
" The use of moving film can be extended by modification of the drive speed to
systems with rotation about other axes, in which the image is not stationary.
As in the periphery camera such a drive can be correct for only one particular
magnification; linear distrotion and possibly unsharpness resulting at other
image scales. The correct film drive speed (Vf) to match the image movement is
given by the formula:
Vf = 2piR [d-(d-v)(1+m)]
where R is the rotational speed of the camera
d is the distance of the axis of rotation _in front_ of the image point
(this is "negative" if axis of rotation is behind film plane)
v is the image distance from the lens rear nodal point
m is the magnification
Note that when d = v (ie the lens rear nodal point is on the axis of rotation)
Vf = 2piRd (or 2piRv)
and is independent of magnification.
Also, when m is small, as with distant objects:
Vf = 2piRv
and is independent of the axis of rotation."
... does this answer your question? ;-)
Andrew Davidhazy, andpph@rit.edu
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From: Kevin Mackenzie
Subject: Re: Panoramic Cameras
Thanks very much for your reply; It does indeed answer my question. I am
thinking about mounting an old rangefinder upside down on a wooden disk. This
disk could then rotate on a bearing above another disk with an elastic band
around it to act as a tire. The film rewind knob could ride on this tire. Now
by having the circumference of the disk and tire sized appropriately, the
correct length of film could be drawn past a slit at the film plane. I assume
that if I do not correct for the off axis-nis of the film plane then distortion
would be greatest very close to the camera and much less as distance increases.
I can tolerate this and any of my slighty overweight (and wide) friends could
be positioned slightly closer to the camera than the thin folk :-)
A panoramic photo of the stars would be really great. Perhaps this could be
done from earth near one of the poles during winter (night). This could be
done with a regular camera and tripod if the speed of film rewind could be
accurately controlled (over a 24 hour period), the earth would provide the
rotation.
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Note 32.04 -< Pointers on drying Fiber Based papers >-
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Your print drying method is important because it affects the final surface.
The simplest but slowest technique is air-drying. You must first remove
surplus water from back and front print surfaces with a rubber squeegee.
Leave prints on absorbent material such as cheesecloth or photographic
blotting paper, face up for RC paper, face down (to reduce curl) for hardener
treated fibre prints. Pet them on a line with plastic clothes pects at top
and bottom - fibre prints in pairs back to back, RC prints singly. Drying may
take several hours at room temperature.
To speed up drying of RC prints, hand them in a heated film drying cabinet, or
blow them over with a hair dryer (termperature not exceeding 85C. Better
still, pass the wetted prints through an RC dryer, designed to deliver dry
prints in about 10 seconds.
For fast drying of fibre prints, have a flat-bed or rotary glazer, which uses
canvas to press the paper against a heated (usually polished chrome) metal
surface. Placing the back of the print towards the heat gives a final picture
surface similar to air drying. However, to get a glazed finish with glossy
fibre paper, you squeegee it face down on to the chrome sheet, so the gelatin
supercoat sets with a matching mirror-like finish when dry. Unless this is
done, glossy fibre papers will dry semi-matt. You can at any time remove the
glaze by thoroughly resoaking the fibre print and then drying it faced the
other way. (Avoid hot-glazing other fibre paper surfaces, and RC prints of
any kind. The former take on ugly patches of semi-glass, the latter will melt
at 90C or over and adher firmly to the metal and canvas.)
Manufacturers of premium fine-art fibre papers recommend air drying unless you
are glazing glossy. The fact is, anything touching the emulsion during drying
is a potential source of damage. There is always a risk, when using a glazer
for other fibre paper surfaces, that the canvas will either mark the final
emulsion finish, or chemicals previously absorbed from drying insufficiently
washed prints will transfer into your print. However, this is still the best
drying method for thin-base prints, which tend to curl badly if air-dried
instead.
Not all my own work. mary :)
From: cmamjt@soc.staffs.ac.uk (Mary Thomas)
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Note 32.05 -< Dividing 1 gal E-6 for small batch processing >-
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For those wishing to make up Kodak E-6 chemistry for small batch processing
in 500 ml tanks, I offer the following dilutions for each of the steps that I
used successfully for years (while processing one to 2 rolls at a time by hand)
Add to 200 ml of water at room temperature...
First developer 86.55 ml
Reversal Bath 29.56 ml
Colour developer
A 83.03 ml
B 29.56 ml
Pre-bleach 84.47 ml
Bleach
A 236.5 ml
B 7.378 ml
Fixer 59.125 ml
Final rinse 3.68
Note: ALWAYS add colour developer A BEFORE B, and ALWAYS to a dilution with
water. NEVER add the A to the B or there will be a precipitate that will not re
dissolve. When purchasing the 1 Gallon Kit I also used to purchase an extra
bottle of first developer as well as an additional colour developer to extend
the number of rolls I could process from the kit (the bleach being the most
expensive part).
Take note that after the carefully added aliquot (gotta love that word eh?) of
the E-6 chemistry to the 200 ml of water at room temperature .....
BRING THE VOLUME UP TO 473 ml, (1 pint US)
This one pint of developer will process a total of 4 rolls of film
The first two rolls will be developed for 7 minutes at 100 deg F and the
second two rolls should have the time extended to 7.5 minutes.
Ken Sinclair RBP., Agriculture and Agri-Food, Canada Research Centre,
Lethbridge, AB. Canada, (403) 327-4561. x 306, Sinclair@abrsle.agr.ca
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Note 32.06 -< High Speed Photography Sample Exam - Questions and Answers >-
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This is a sample exam associated with a high speed photography course in the
Imaging and Photographic Technology program in the School of Photographic Arts
and Sciences at RIT. It is given in the early parts of the course (when some
of the topics have not yet been covered) so that students will get a general
idea of what the style of the final exam will be. In some cases a variation on
these same questions is included in the final, in others the questions are not
included in the final. Following the distribution of these questions the
instructor briefly goes through the answers to each question but does not
dwell on the theory that has not yet been covered since this willbe eventually
covered in the course. Listed below first are the questions by themselves and
below them are the questions followed by the answers.
1 What is the exposure time necessary to limit blur in a subject moving at
10 feet per second to 1/100 of an inch at the film plane if you used a
50mm lens and the subect was 2000mm from the camera?
2 Photographing a TV screen with a Focal Plane will produce a raster
pattern that is similar to that produced by a Leaf Shutter shutter when
what condition is established?
3 What is the limiting or defining criterion that defines whether a
photographic print appears sharp or not?
4 If an electronic flash circuit is able to handle the change, then what
is the effect of doubling the voltage of the circuit?
5 What is the effect on the duration of the flash given the same conditions
as in the previous question?
6 Why is it not practical to measure the duration of an electronic flash at
50% output levels?
7 What kind of synchronizer would you use to photograph the splash produced
by a falling drop of milk and why?
8 A synchronizer that depends on detecting the sound emitted by an even
does not allow you to photograph what portion of the event?
9 A streak camera is capable of measuring several factors associated with
subjects. Name at least three of them.
10 What steps would you take in order to make measurements based on a streak
camera, or any other camera for that matter, independent of magnification.
11 A picture is made at an exposure time of 1/100 second with a 35 mm camera
equipped with a leaf-shutter and a 50mm lens. The picture that you make of
a 1 foot square subject appears as an image that is twice as long as it is
tall. From this you can deduce that the subject was moving at what speed?
12 In a streak camera in which the film is moving at 35,000 mm per second a
subject that moved at right angles to the film motion leaves a 45 degree
trace across the width of the film. How fast was the image of the suject
moving?
13 In order to calibrate anything you first need what?
14 With a focal plane shutter, exposure time is defined by what relationship?
15 Assuming that two photographs of the same moving subject are made one with
a 100 mm lens and the second with a 50mm lens. The prints show the subject
the same size. One photograph, made with a 100mm lens, exhibits motion blur.
Describe the appearance of the second photograph concerning the same effect.
16 The maximum framing rate at which a camera can usually operate is a
function of how fast the film can be advanced and the shutter recocked in
the camera plus another factor. What is this "other" factor?
17 These are a series of images made sequentially with a camera making
1000 pictures per second of a rotating fan. Assuming that the fan turns
less than one revolution between pictures, at what rate was the fan turning
in RPM?
.------..------..------..------..------..------..------..------.
| | || / || || || || || ||\ |
| | || / || ---|| || || ||__ || \ |
| || || || || \ || | || || |
| || || || || \ || | || || |
------ ------ ------ ------ ------ ------ ------ ------
18 Moving a sound synchronizer's microphone 1 foot further away from the
source of sound will add about how much delay to the next photograph?
19 The slope of the edge of a shock wave is a function of the speed of sound
in the gaseous medium in which a missile moves and the...
1 What is the exposure time necessary to limit blur in a subject moving at
10 feet per second to 1/100 of an inch at the film plane if you used a
50mm lens and the subject was 2000mm from the camera?
The answer to this question is based on Image/Subject distance relationships.
If the lens is a 500 mm lens and the subject was 2000 mm from the camera then
the Subject is 2000/50 or 40 times bigger than the image made by the lens. If
the blur can only be 1/000 inch in the camera, at the Subject this translates
to 40/100 or .4 inch. So the Subject can only move .4 inch during the exposure.
Since the amount of Blur one gets is determined by taking the Subject Speed or
Velocity and multiplying by the Exposure Time this can be rearranged so that
Exposure Time required is equal to Blur Allowed divided by Subject Speed.
so, required ET = .4 inches divided by 120 inches per second or 1/300 second
2 Photographing a TV screen with a Focal Plane will produce a raster
pattern that is similar to that produced by a Leaf Shutter shutter when
what condition is established?
A TV set delivers 15,750 lines of information on the screen per second. That is
there is 1/15,750 second between lines. Theoretically one should only "see"
15.75 lines of the screen if one makes a picture at 1/1000 second. This is more
or less so but due to afterglow of the phosphors in a practical situation it is
a bit off. Anyway, the lines are laid down from top to bottom. If photographed
with a leaf shutter one sees a horizontal "band" 16 or so lines wide. If
photographed with a Focal Plane shutter lined up to travel horizontally with
respect to the scanning direction will show a diagonal "band" still 16 lines
wide at each end.
If the FP shutter travels parallel to (either with or against) the direction
of motion of the CRT scan the result will be a pattern very similar to the one
produced by the leaf shutter but it will depict fewer or more lines than should
be counted as a result of the exposure time given by the shutter.
3 What is the limiting or defining criterion that defines whether a
photographic print appears sharp or not?
for imperceptible blur in a print the defining criterion is the maximum
acceptable size of the circle of confusion under the given conditions.
4 If an electronic flash circuit is able to handle the change, then what
is the effect of doubling the voltage of the circuit?
Potential power or watt.second rating of a flash is given by 1/2 Capacitance
times Voltage Squared therefore doubling the votage quadruples the power
5 What is the effect on the duration of the flash given the same conditions
as in the previous question?
Half-peak to half-peak duration is specified as Capacitance times Resistance
divided by square root of two. Therefore upping the voltage does not affect
duration.
6 Why is it not practical to measure the duration of an electronic flash at
50% output levels?
This gives an "inflated" estimate of action stopping ability of an electronic
flash. It basically neglects light emitted by the flash before and after the
light level is at the 50% output level. It assumes that underexposure of a
scene by one stop (50%) does not produce a useful record when we all know that
one can underexpose by several stopsand still get some sort of an image.
The result typically is that highlights of a moving subject appear
significantly more blurred than shadow areas since the light level has to drop
many stops lower than full intensity before it is low enough to not produce
significant exposure to the film.
It is much more "practical" to estimate the duration of electronic flashes at
25% or even 10% percent output levels.
7 What kind of synchronizer would you use to photograph the splash produced
by a falling drop of milk and why?
A "dark" synchronizer. A drop passes through a light beam changing a "light"
condition into a dark one. This is detected by a circuit which causes a flash
to fire. It helps if the signal from the "dark" synchronizer is delayed a
(variable) fraction of a second to give the drop a chance to fall to a more
useful location than the light beam which is used to detect its passage.
If the "dark" sync trips an SLR some measure of dealy is introduced by the
camera itself since they have an inherent delay before releasing the shutter
curtains and since the flash does not fire until the first curtain has actually
travelled across the frame even more delay is potentially available. The actual
pattern of the splash can then be adjusted by raising or lowering the impact
surface.
8 A synchronizer that depends on detecting the sound emitted by an even
does not allow you to photograph what portion of the event?
The beginning. By the time you hear it, the beginning of an event is over.
9 A streak camera is capable of measuring several factors associated with
subjects. Name at least three of them.
Elapsed Time Velocity Acceleration Frequency Simultaneity
10 What steps would you take in order to make measurements based on a streak
camera, or any other camera for that matter, independent of magnification.
Include a scale or subject of known size in the picture and then make
measurements within the picture based on the reproduced size of this scale.
11 A picture is made at an exposure time of 1/100 second with a 35 mm camera
equipped with a leaf-shutter and a 50mm lens. The picture that you make of
a 1 foot square subject appears as an image that is twice as long as it is
tall. From this you can deduce that the subject was moving at what speed?
If the subject is 1x1 foot and it appears to be twice as long as tall then the
Subject would be 1x2 feet. Subtracting out the first foot (the size of the
subejct itself) gives an indication that the subject moved 1 foot during the
exposure time or in 1/100 second.
therefore, if it moved 1 foot in 1/100 second it was moving at 100 feet/second
12 In a streak camera in which the film is moving at 35,000 mm per second a
subject that moved at right angles to the film motion leaves a 45 degree
trace across the width of the film. How fast was the image of the suject
moving?
For every unit of film that moved through the camera one unit of image moved at
right angles to the direction of motion of the film. Therefore the veolcities
of the film and image were the same. So, 35,000mm second was the image speed.
13 In order to calibrate anything you first need what?
a standard
14 With a focal plane shutter, exposure time is defined by what relationship?
The ET of a focal plane shutter is equal to the width of the slit divided by
the rate at which the slit moves.
15 Assuming that two photographs of the same moving subject are made one with
a 100 mm lens and the second with a 50mm lens. The prints show the subject
the same size. One photograph, made with a 100mm lens, exhibits motion blur.
Describe the appearance of the second photograph concerning the same effect.
The two pictures will essentially be identical in terms of motion blur but
since the one made with the 50 mm lens will have to be blown up twice as much
as the one made with the 100 mm lens it will appear "grainier".
16 The maximum framing rate at which a camera can usually operate is a
function of how fast the film can be advanced and the shutter recocked in
the camera plus another factor. What is this "other" factor?
Assuming one is not allowed to start making a picture before one is done making
the previous one the ultimate limiting factor in terms of recording frequency
is the EXPOSURE TIME.
17 These are a series of images made sequentially with a camera making
1000 pictures per second of a rotating fan. Assuming that the fan turns
less than one revolution between pictures, at what rate was the fan turning
in RPM?
.------..------..------..------..------..------..------..------.
| | || / || || || || || ||\ |
| | || / || ---|| || || ||__ || \ |
| || || || \ || | || / || || |
| || || || \ || | || / || || |
------ ------ ------ ------ ------ ------ ------ ------
1 2 3 4 5 6 7 8
Note that the fan blade turns 180 degrees between picture #1 and picture #5
That means that 5 - 1 pictures, or 4 pictures were required to record these
180 degrees. Picture #1 is simply the reference mark. Therefore the fan
turned 180 degrees in 4/1000 or 1/250 second. That is 180 x 250 or 45000
degrees per second which is 7500 RPM
18 Moving a sound synchronizer's microphone 1 foot further away from the
source of sound will add about how much delay to the next photograph?
Since sound travles at about 1000 feet per second, 1 foot stands for 1/1000
second.
19 The slope of the edge of a shock wave is a function of the speed of sound
in the gaseous medium in which a missile moves and the...
velocity of the missile itself. Thus the angle of the shock wave (which can
be relatively easily recorded with a shadowgraph system) can be used to make
a good estimate of the speed of a missile.
Andrew Davidhazy, at RIT's Imaging and Photo Tech Dept, andpph@rit.edu
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Note 32.07 -< The Royal Photographic Society - Info >-
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>I would like to take up the Licentiateship of Royal Photography Society,
>But I do not have the Address . If you could get it to me I'd appreciate it.
The best source of information is a 16 page special feature 'Gaining RPS
Licentiateship' in the July/August 1994 issue of The Photographic Journal
(ISSN 0031-8736), (which is the Society's Journal).
The appropriate application form for Licentiateship can be obtained from:
Ms Carol Agar
The Royal Photographic Society
The Octagon
Milsom Street
Bath BA1 1DN
UK
Phone: 0225 462841
(The RPS, like many UK institutions, is not (yet) on the Net!)
There is also an information booklet available from the above, giving full
details of the requirements for the Licentiateship and for all the
categories of each RPS Distinction.
From: Mike Ware
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Note 32.08 -< More panoramic photography material ... >-
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>I am thinking about trying to make a simplified ciircuit camera. For those
>who do not know a circuit camera is one where the lens rotates and "paints"
>an image across the film as it rotates. These were used a lot in the past
>to take panoramic pictures. I know of only one currently made.
The "cirkut" camera is undergoing somewhat of a revival in terms of new models
being available. Not in the large formats of the past but in 16mm, 35mm,
120/220, and 70mm. There was even a recent attempt at a 5" sized one.
Hermann Seitz of Switzerland (?) manufactures several models starting from
16mm. Alpa makes (made?) the Rotocamera that is either 120 or 70mm. On the
American side there is(was?) the Globuscope in 35mm and the Hulcherama in the
120 size. Globus also made an adapter for a 4x5 camera that used 5" roll film.
I believe they made 1 or two of them! And who can forget the one made by
Corrales Cameras, the 35mm SpinShot, a plastic wonder at $ 720 for 360 degrees?
There may be a couple more models as well.
There is a very active group of amateurs and professionals that use, rebuild
and build "cirkut" type and swing-lens panoramic cameras. It is the
International Panoramic Photographers Association.
I myself am one of those amateur builders and experimenters. My cameras are all
35mm. I have made them based on rewinding the film to move the film past a slit
and have also made some based on advancing the film with the sprocket drive and
providing power to the sprocket either through motors or by direct coupling
with a gear or friction drive arrangement. I have also published several
articles on the application of "strip" cameras from use in the panoramic mode
as well as the peripheral, photofinish and aerial/terrestrial scanning modes.
>I am interested in the physics of how the images is made by the rotating
>lens and how the exposure time can be calculated. How do you relate
>the speed of rotation of the lens to an actual shutter speed?
Basically the length of any panoramic photograph is governed by the focal
length of the lens you choose. Once the length is known then the time to cover
the desired angle will determine the rate at which the film must move throught
he camera. Once this rate is known, then the width of the "shutter" slit
divided by the rate of film motion gives the exposure time. Once this is known
then you take a meter reading and determine the aperture required for the given
exposure time and then you take your picture.
Roughly speaking the camera is typically rotated about a point located near the
rear nodal point of the lens or somewhat closer to the film than this point.
This causes the image formed by the lens to remain stationary in space behind
the lens even as the camera is turning. The function of the film is to simply
move at the same rate as the image seems to be left behind by the moving slit
so that it will remain stationary with respect to the image. It is amazing how
well the system works.
To determine exposure time this is one approach.
For example: Assume you will make a panoramic camera of this kind using a 24mm
lens as the camera lens. A full 360 degree shot with it will require
2 x pi x f mm of film or 2 x 3.1416 x 24 = 150mm
now say you want to cover the 360 degrees in 10 seconds, then
Film Velocity in camera = 150mm / 10sec = 15mm/sec
if you then know that the stationary shutter slit in the camera is 1mm in width
Exposure Time = slit width / film rate 1mm / 15mm/sec = 1/15th second
As I said this is one way to do it. There are others but they all lead to the
same place.
There are two unusual home-built panoramic cameras that to the best of my
knowledge are of a unique design. One was built by Phil Foss of Kodak and the
other by myself. They both operate by placing their image on film rotating at
the film plane instead of moving in linear fashion. While Phil's typically is
designed to cover a full 360 degree circle, mine can place a 360 degree pan on
less than a 360 degree tyrn of the film. This allows the shaping of the
resultant panoramic images to be made into conical shaped products such as flat
sunhats, umbrella decorations, skirts, or lampshades.
The history of the evolution and development of the camera was presented at a
meeting of the SPIE, the International Society for Optical Engineering. If you
would like a reprint of the paper just send me your postal, snail mail, address
and I will ship one out to you until supplies last. After that it's copies!
(You can get the text copy of this paper from the ARTICLES available from
ritphoto@rit.edu)
BTW, there are several members of the IPPA who have made exquisite panoramic
cameras on their own. Steve Morton from Australia is one. Jim Lipari is
another. Among the earliest makers of continuous enlargers at the amateur level
are the machines built by Foss and myself. But of course we were preceeded by
the designs that Itek Corporation used to make a continuous enlarger for the US
Air Force in the mid to late 1950's.
BTW, BTW... these cameras are close cousins to peripheral cameras used to
document ancient vases with designs surrounding their periphery. These were
made by the British Museum in the late 1800's. They are also related to
photofinish cameras althogh these were not introduced into use at tracks until
the mid 1930's. DeVeccio (sp) and Western Electric disputed the ownership of
the original idea. But of course the Cirkut camera had them "beat" since it
came about in the late 1800's and was commercially available from Kodak from
the early 1900's to about 1940 or so.
BTW, BTW, BTW you can expect to see a relationship between these cameras and
something called, in electronic imaging terminology, Linear Arrays. A CCD array
consisting of only one row of pixels. Also related to the word "scanning" that
we have all become so familiar with. Scanning in photo terms was never very
popular but everyone seems to appreciate the word in its "electronic" context.
Interesting! To appreciate what these cameras do next time you are near a
"moving light wand" type copier make yourself a copy of your hand both while
you keep it satitonary and also while you move it along with, against or
sideways as the copy is being made. Scanningly educational activity, this!
regards,
Andy, andpph@rit.edu
================================================================================
Note 32.09 -< How to determine the aperture and f# of a lens? >-
--------------------------------------------------------------------------------
>Is there any simple way to figure out the *true* aperture of a lens? I know
>that focal length/diameter of front element is an approximation, but how good
>an approximation.
Size of the front element has nothing to do with the aperture (well it does
have some relation to aperture, but no direct relationship). Filter threads are
often standardized by manufacturers to simplify things like filters, lens caps
and probably other manufactured parts used in the construction of the lens.
The aperture is the focal length divided by the diameter of the physical
aperature (as seen from the back so it may be affected by the optics to be
something different from the physical aperture, particularly in something with
a telephoto design). One way of determining the actual aperture is to place a
pinhole at the film plane with a very bright light shining through the pinhole.
With the lens focused at infinity, a card held in front of the lens will
produce a spot on the card the size of the aperture as seen by the film. You
can then sort of measure this spot and calculate the actual aperture from the
focal length and your measurement. If you do try this, be very careful because
the bright light can easily melt or burn something in the back of your camera.
John Sparks, sparks@col.hp.com
Subject: Is there an easy way to calculate a lens' aperture?
Organization: HP Colorado Springs Division
...............................................................................
Correct me if I'm wrong, but doesn't this assume two things:
1) That the given focal length of the lens is accurate
2) That the lens does not over-focus at infinity
In other words, if your 135mm/f2.8 lens is really closer to 133mm, your
measurements will be slightly off. As an example, if your lens were
truly f2.80, then a 135mm focal length should give you a spot that was
48.21mm in diameter (if my math is wrong, someone do the calculations).
If your lens is actually 133mm, then you'll get the same 48.21mm spot,
but your aperture will now be calculated as 2.76.
Second, if the lens over-focuses at infinity (most telephoto lenses do,
to accomodate for lens shrinkage/expansion in cold/heat), then two
things happen: First, your focal length decreases, and second, you're
not measuring a true infinity focus.
Small things, but if someone is trying to accurately determine their
aperture with any great precision, these things do need to be taken
into account.
I know how to deal with the second one (focus on the moon. poof!
You're at infinity focus). The first one, I would approach by doing
some painstaking macro work. Take your lens at infinity focus (ha!)
and maximum aperture (again, ha!) with a +4 diopter lens on it. Take a
picture on slide film of something with a known, accurate length (a
good millimeter reference would be nice). Measure the image on the
film to determine magnification ratio. From that, you can calculate
the "true" focal length of the lens to some amount of precision.
Whew. Too much math for me in one day. :-) I'm done.
ECLDCO@ritvax.isc.rit.edu
.............................................................................
ECLDCO,
In other words, I think we are saying the same thing when I say that
_if two lenses are truly f:2.8_ then the aperture of a 135mm lens is
48.2mm and the aperture of a 133mm lens is then 47.5mm.
OTOH, if the effective apertures are the same 48.2mm, then a 135mm lens
will have a f# of 2.8 while another one, which may have a focal length
of only 133mm would have an f# of 2.76
Whether one can accurately measure spot sizes to within 2/10mm accuracy
is something else again. In fact, the procedure of projecting light
backwards through the optical systemdoes depend on accuarcy on the size
of the pinhole at the image plane. Once it gets too large the edges of
the spot start to get too fuzzy to accurately determine the diamter of
the spot.
I think the poster of the previous article was a bit misleading in
refering to the size of the aperture as seen from the rear. This is
true but the f# is determined by dividing the focal length by the
diameter of the "entrance pupil". That is why the method for
determining its diameter by shining a light "backwards" through the
system is appropriate. The spot you will see is an indication of the
size of the front or entrance pupil.
He did mention (I believe) that you would have the lens focused on
infinity. By definition therefore any lenses that are not focused on
infinity first need to be adjusted for that condition. When a complex
zoom or tele lens "over-focuses" as you state it is obviously not
focused at infinity.
Since a knowledge of the focal length is important you are absolutely
correct in stating that you must either assume it is correctly marked
on the lens, that is is within acceptable limits or determine it for
yourself.
The best method for determining focal length is through use of a nodal
slide. As for determining the focal length of a lens by focusing on
a nearby object using the +4 diopter lens as the basis for the
calculation that depends also on assumptions that it is indeed a +4 and
not a +4.1 diopter lens or some such variant. In fact, it may be easier
to do this with a +1 lens whose focal legth you can more easily measure
by focusing it on a distant object and measuring from the center of the
glass to the image plane.
Another variation is to accurately measure the size of your image gate
in the camera. Lock shutter open and placing a groundglass in the film
plane then aim the camera at some distant object and line it up so that
the object lies at one edge of the frame. Draw a line on a pice of
paper below the camera body using the base of the camera for a ruler.
Then swivel the camera in the opposite direction so the object now is
coincident with the opposite edge of the gate. Draw another line as
before intersecting the previous line. Remove camera. Bisect the angle
betwee the lines and "move" a line perpendicular to this one and equal
to the size of the image gate in your camera, until it touches the two
lines drawn on the paper. Once this is set up measure from the
intersection of the lines to the line representing your image gate and
that will be the focal length. (to some amount of precision also)
Ultimately, whether an error of 2.8 vs 2.7 or even 2.5 is significant
is a matter that is so dependent on accuracy throughout the system as
to often not being meaningful at all since there are so many errors
that can creep into the photographic process. You just hope that they
don't all add up in a single direction all at once! (This last statement
is more a statement of philosophy than anything else)
cheerio,
andy, andpph@rit.edu
...............................................................................
With multi-element telephoto designs this rule of thumb (focal length divided
by diamter of fron element)will tend to give a lower (ie faster) f-number than
the true value, because the front element is enlarged to minimise vignetting.
The figure you really want is the diameter of the entrance pupil which can be
estimated by holding the lens up to the light, with the front element towards
you, and measuring the size of the aperture in the lens as it appears from the
front. This doesn't work well for very short focal- length lenses - see David
Jacobsons lens tutorial for more information, and Rudolf Kingslake "Lens Design
Fundamentals" for lots of details.
Only ray-tracing or very careful experimentation can determine the true f-ratio
at different points in the image. For interest, here's some measurements off a
couple of lenses I have here:
Lens Front element Entrance pupil
35mm, f/2 26mm (f/1.3) 16mm (f/2.2)
100mm, f/2.8 35mm (f/2.9) 32mm (f/3.1)
Christopher
=======================================================
Christopher Hicks http://www.eng.cam.ac.uk/~cmh
cmh@eng.cam.ac.uk Voice: (+44) 1223 3 32767
=======================================================
================================================================================
Note 32.10 -< Pointers for including the moon in a photograph >-
--------------------------------------------------------------------------------
> I need some suggestions in photographing a rising full moon.
This advice works for a full moon high in
the sky. But when the moon is near the horizon, it may be much dimmer,
depending on the atmospheric conditions in the area. The "Loony 11" rule
(1/(film speed) at f/11) will give the _least_ exposure likely to give a good
full moon. Bracket from there toward longer exposures. For an orange moon on
the horizon, I'd go several stops toward more exposure.
Be careful not to let your exposure time go beyond a second or so if you want
any detail of the moons surface. The moon traverses its own diameter in the sky
every 3 minutes or so. Motion blur will be significant with longer exposures.
Then again, if there's enough stuff in the atmosphere to make the moon orange,
you probably won't see any surface detail anyway. Exposures above 15 seconds or
so will make the moon look oblong. If foreground isn't an issue, open up your
aperture rather than use longer exposures. Depth of field usually isn't an
issue when your subject is 240,000 miles away.
It takes a longer lens than you'd imagine to make the moon look as large as
you'd expect in the frame. To fill the frame on a 35mm camera, you'd need about
a 2500 mm lens. (Note: There's a popular misconception that a 1000mm lens is
about right to fill the frame with the full moon. It's wrong.) One popular (and
maybe overdone) technique to deal with this (as most of us don't have 2500mm
lenses) is to do a double exposure. Expose the full moon in one part of the
frame with a 300 or 400 mm lens. Then expose some other picture with a shorter
lens on the same frame. It will help if the area occupied by the moon in the
second scene is black sky. This "oversized" moon effect helps compensate for
the tendency for the moon to look too small in normal photographs.
And finally, it's difficult to catch a rising full moon on the horizon and
compose it in a scene. The trick is to predict where it will break the horizon.
Even if you can do that, cloud cover often obstructs the moon until it's a few
degrees up. One pretty good approximate way to predict the point of moonrise is
to note that the full moon will rise almost exactly opposite the point of
sunset. As the sun goes down and shadows get long, the shadows will point to
the approximate point where the moon will rise a few minutes later. The time of
moonrise is about 50 minutes later than the time it rose the night before. Or
you can look in your newspaper. The time of moonrise is often given on the
weather page. Good luck,
Dave Boyd, daveb@gr.hp.com,
Hewlett-Packard, Greeley, Colorado
Standard Disclaimers Apply
================================================================================
Note 32.11 -< Sun and Moon rise/set locator program retrievable from Net >-
--------------------------------------------------------------------------------
If you would like to know where (Compas Setting) and when (Time) the sun
or moon will rise or set ftp to:
ftp.funet.fi/pub/astro/prog/win
and download the files
alw113a.exe and alw113b.exe
The planetarium program will tell you the compas location next to Azi:
The rise and set dates and times are under Calendar
From: snapshot35@aol.com (SNAPSHOT35)
=========================== end of section 32 ==============================
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